1. Field of the Invention
The present invention relates generally to can manufacturing tool pack assemblies that have drawing and ironing dies for reforming a cup into a container body, and more specifically to such a tool pack assembly that is internally cooled.
2. Brief Description of the Related Art
Can forming dies are used to form the bodies of metal cans or containers. The description herein is particularly concerned with forming two piece metal containers. A shallow metal cup is driven into the dies by a punch to form the body of the can. The dies generally are provided in tool packs in which a series of progressively narrower die nibs are arranged to progressively draw and iron the metal cup into a container of the desired shape and thickness. An example of a conventional set of drawing and ironing dies in a tool pack is shown in U.S. Pat. No. 4,173,882 issued to Lee, Jr. on Nov. 13, 1979, the entire disclosure of which is incorporated herein by reference. Each die is included in a respective die module.
Die tool packs used in commercial can manufacturing conventionally use cooling fluids applied to the exterior of the die pack to maintain or reduce operational temperatures of the dies. In certain can forming applications, however, it is desirable to avoid the use of external cooling fluids. For example, external cooling fluids may contaminate the container surfaces, which requires costly and environmentally undesirable post-formation cleaning processes.
The present invention overcomes the disadvantages of the prior art, such as those noted above, by providing an internally cooled modular die tool pack assembly that does not require the use of cooling fluid applied to the exterior of the tool pack. Instead, the temperature of the tool pack is controlled by forcing a fluid, particularly a liquid, with desirable heat transfer properties around the die nibs through special die cavities and heat is transferred by conduction. The external temperature of each die nib can be monitored continuously at the respective die module, and the fluid medium temperature can be adjusted automatically to maintain acceptable die temperatures.
The fluid medium is supplied to the tool pack by a temperature control unit, and is delivered to the die modules by a series of pipes, fittings, and hoses. Fluid medium flows through porting in each module and its die where the fluid is directed circumferentially around the outer surface of the die nibs. Preferably, multiple porting in each die is circumferentially symmetrical, with alternating inlet and outlet ports to distribute the fluid medium uniformly around each die nib. The multiple fluid inlet and outlet design with symmetrical porting assures that all of the die nib temperatures remain substantially uniform, and also minimizes temperature gradients around the die. In a preferred embodiment, four inlet ports and four outlet ports are provided with inlet and outlet ports alternating at 45xc2x0 apart. But the number and placements of ports can be altered to address specific temperature control requirements.
Other features and advantages of the present invention will become apparent from the following detailed description which refers to the accompanying drawings.